Hello GHC hackers, I have been trying the recent 7.4.1-rc1 release on my OSX Snow Leopard machine. I am using the 64bit OSX .tar.bz. I used virthualenv/hsenv to set up a virtual environment to test packages with the RC, but I discovered that GHCi seems to segfault somewhat randomly when invoked. I cannot reproduce this problem with 7.0.4 (64bit,) 7.2.2 (64bit,) or 7.5.20111223 (also 64bit.) I have invoked GHCi probably a hundred times each, and have never had it crash. I can crash the RC fairly reliably however. I looked at the shell scripts that invoke GHC and ran GDB with the proper arguments. I got a backtrace like so: $ gdb /Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219/ghc GNU gdb 6.3.50-20050815 (Apple version gdb-1518) (Sat Feb 12 02:52:12 UTC 2011) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "x86_64-apple-darwin"...Reading symbols for shared libraries .... done warning: Could not find object file "/Users/ian/zz64/ghc-7.4.0.20111219/rts/dist/build/libHSrts_thr.a(ffi64.o)" - no debug information available for "../src/x86/ffi64.c". warning: Could not find object file "/Users/ian/zz64/ghc-7.4.0.20111219/rts/dist/build/libHSrts_thr.a(prep_cif.o)" - no debug information available for "../src/prep_cif.c". warning: Could not find object file "/Users/ian/zz64/ghc-7.4.0.20111219/rts/dist/build/libHSrts_thr.a(types.o)" - no debug information available for "../src/types.c". (gdb) r -B/Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219 --interactive Starting program: /Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219/ghc -B/Users/a/vh-741-rc1_2/.hsenv/ghc/lib/ghc-7.4.0.20111219 --interactive Reading symbols for shared libraries + done GHCi, version 7.4.0.20111219: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x00000000ae21cf68 0x00000001ae2060da in evacuate1 () (gdb) bt #0 0x00000001ae2060da in evacuate1 () #1 0x00000001ae20b868 in scavenge_block1 () Previous frame inner to this frame (gdb could not unwind past this frame) (gdb) So it looks like a GC bug at first glance, but I haven't done rigorous investigation. Again this doesn't happen every time - probably 1/3 the time it crashes, the other 2/3 the time it seems to work fine. This naturally also affects `runghc`. Is this a known issue? Or should I file a bug and investigate further? Perhaps something forgot to get something merged into the 7.4 branch? -- Regards, Austin